A lens that has a refractive index that varies in a controlled way throughout its body is referred to as a gradient refractive index (GRIN) lens. The refractive index typically changes as a gradient, in that it varies gradually throughout the body of the lens. The naturally occurring human crystalline lens is an example of a lens having a gradient of refractive index.
Production of a single piece foldable multifocal gradient intraocular lens (IOL) has been reported wherein the IOL was manufactured with step-by-step polymerization technology in transfer molds of photohardening material (ultraviolet light) with various refraction indices (oligourethan-methacrylate). See Malyugin et al., Middle East Afr. J. Ophthalmol. 2014 January-March; 21(1): 32-39. This technology can produce multifocal artificial lenses with gradient optics. However, the manufacturing process combines stages of material polymerization with lens manufacturing concurrently.